Resonator measurements and modeling of the low-frequency sound speed of seagrass leaves

Abstract

Previous investigations of seagrass have revealed acoustic phenomena that depend on the material properties of the plant tissue and gas contained within the lacuna of the leaves. However, the application of predictive models to describe these observations has been limited to effective medium models that neglect both the effects of elastic properties of seagrass tissue as well as its structure. To address this, we developed a physiological model of a seagrass leaf that includes the epidermis, a continuous layer on the surface of the leaf that provides rigidity, and the aerenchyma, a soft plant tissue containing the lacuna. To validate the seagrass leaf model, acoustic resonator experiments were performed to measure the low-frequency sound speed of seagrass leaves, and the physical dimensions of the epidermis and aerenchyma were assessed through the examination of microscopic images of leaf cross sections. Using this imagery, a finite element model of the seagrass leaves was created, and COMSOL was used to simulate the resonator experiment. The comparison of the measured and modeled acoustic data provides insights into the parameters of the seagrass tissue that affect the acoustic response, specifically the shear moduli of the epidermis and aerenchyma. [Work supported by ARL IR&D and ONR.]